Lock-in augmented XIVA significantly improves the sensitivity of the system through the implementation of a lock-in amplifier. The lock-in amplifier modulates the laser signal while sampling the output of the XIVA sensor. Utilizing this technique, we are able to realize a Q greater than 100,000.
 
The lock-in amplifier system consists of five major components:
  • Input Signal
  • Reference Signal
  • Mixer/Multiplier
  • Integrator/Low Pass Filter
  • Voltage Amplifier
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The input signal (  ) is the signal sample from the device or system under test.
 
The reference signal (  ) is the signal generated by the lock-in amplifier.
 
The multiplier is essentially a mixer where the input signal and reference signal are mixed to produce the sum and difference signals. The output of this multiplier is can be represented by the following formula: